Radiation exposure in scoliosis surgery – Is it a concern?

4th May 2012

535

A small study, presented at Britspine (2–4 May 2012, Newcastle, UK), has found that the level of intraoperative radiation is low during scoliosis surgery.

Nicholas McArthur and John Crawford, Neurosurgery and Orthopaedic Departments, Addenbrookes Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK, designed a study to assess radiation exposure of both patients and surgeons in scoliosis surgery. Very few publications have dealt with this matter so far.

Study presenter McArthur said that it was a prospective study that took place over a six-month period and involved 30 consecutive paediatric patients undergoing scoliosis surgery (with two surgeons, John Crawford [JC]and David Conlan [DC; also at Addenbrookes Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK], operating on each case). The mean age of patients was 14 years, mean surgical time was 277 minutes, and the mean number of implants was 16. There were three variables used to assess radiation exposure in the patient: screening time, dose area product, and the Monte Carlo calculation. He said: “The Monte Carlo calculation gives an accurate estimate of the radiation exposure that patients sustain by using a number of variables, which also include the dose area product, the patient’s age and their body mass index.” Radiation exposure in the surgeons was assessed with dosimeters on the hands and thyroid.

McArthur et al found that for patients, the average dose area product reading, per procedure, was 91.3cGycm2, the average screening time was less than half a minute, and the average radiation exposure was 252.9μSv. They also found that with surgeons, after six months, the estimated eye dose of radiation was slightly lower (23.3–38μSv) than the estimated thyroid dose of radiation (36–42μSv). McArthur explained that they were not able to get a radiation reading from the surgeons’ hands because it was so low.

McArthur reported the C-arm’s X-ray tube was positioned next to surgeon JC in 13 patients and next to surgeon DC in the remaining 17 patients. He explained that if you were standing next to the X-ray tube, the average radiation exposure per procedure was 2.07μSv. If you were standing on the C-arm’s screen side, you would be better off as the average radiation exposure per procedure was 0.53μSv. McArthur said: “Now in six months, that would have made a difference of 62μSv vs. 16μSv.”

Overall, each year the surgeon’s risk of cancer would increase by 0.0005% by performing surgery on 60 cases of scoliosis per year. He said: “For the patient, who was undergoing surgery only once, the risk of cancer was 0.001%.”

McArthur added: “We estimated the total body radiation exposure at 130μSv per year. That is less than 1% of the whole body limit for these staff members (ie, surgeons). It is approximately equivalent to 21 days’ exposure to background radiation in the UK. Of course, we need to consider other sources of radiation.”

The study’s conclusion, McArthur reported, was that the overall dose of radiation was “quite low”. He added: “If there are two surgeons operating at the same time, consider swapping sides. If operating alone, be on the opposite side of the X-ray tube.”